Machine for grinding the contact-surfaces of carbon brushes for dynamos and the like.



A. WATKINS.

MACHINE FOB. GRINDING THE CONTACT SURFACES OF CARBON BRUSHES r03 DYNAMOS AND THE LIKE.

APPLICATION FILED JULY 17, 1911.

019 2 1 7 Patented Mar.5, 1912.

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:H g S r 1 5 i1 -1 970 g 6L 0 d UNITED STATES PATENT OFFICE.

ALFRED WATKINS, OF CHELSEA, LONDON, ENGLAND.

MACHINE FOR GRINDING THE CONTACT SURFACES OF CARBON BRUSHES FOR DYN AMOS AND THE LIKE.

To all whom it may concern:

Be it known that I, ALFRED WATKINS, a subject of the King of England, residing at Chelsea, London, in the Kingdom of England, have invented new and useful Improvements in Machines for Grinding the Contact- Surfaces of Carbon Brushes for Dynamos and the Like, of which the following is a specification.

This invention relates to a machine for grinding the contact surfaces of dynamo brushes and the like and has for object to increase the efiiciency and simplify the construction of such machines.

For this purpose the said machine consists of a frame of metal having two arms or sides set at an angle in the form of a V. This frame is carried by a transverse spindle mounted in bearings formed in a stand comprising two side members connected together by cross bolts and nuts, and

between which the said frame oscillates to and fro by means of a handle fixed to the spindle. These side members support a central cross-piece or flanged plate to which is fitted a wooden, or other similar block, curved on its upper surface so as to correspond with the curve or radius or the commutator or other surface, upon which the brush or other tool is to bear. Over this curved surface is tightly stretched, by means of clamping bars, and thumb nuts at each end of the frame, a sheet of glass paper, emery-cloth, or other suitable grinding material. The brush is held in position for grinding by means of a cross-plate carried by two brackets fixed to the side frames, the plate being pivoted to said brackets and being engaged at its upper end with a radial slot in each bracket through each of which passes a wing-nut for fixing it at any desired angle. The brush or tool is held against the pivoted plate by the hand of the operator and at one side against an adjustable guide or block, fixed to the plate, the lower end of the brush bearing upon the grinding paper or sheet so that it is evenly grained upon moving the handle backward and forward and consequently causing the to and fro travel of the said paper or sheet underneath the lower edge of the brush thus effectively grinding the latter to the shape of the segment of the block.

In the accompanying drawings Figure 1, is a sectional elevation of the machine and Specification of Letters Patent.

Application filed July 17, 1911.

Patented Mar. 5, 1912. Serial No. 638,972.

Fig. 2 is an end elevation thereof. Figs. 3 and 4 are respectively a longitudinal section and an end view of a detail.

a is the metal V-shaped frame keyed to the transverse spindle b and mounted in the bearings 0 formed in the stand or outer frame, cl the two side members, which are connected together by the cross-bolts and nuts 6 and f is the handle for operating the frame a.

g is the cross-piece or plate engaging with a recess 9 in each frame (Z so as to be supported thereby.

h is the wooden block fitted thereto and fixed by a screw or screws h, the said block being curved on its upper surface to correspond with the curve of the commutator for which the brush has to be ground. For differently curved commutators the block it may be readily removed, by unfastening the screws, and replaced by a block of the desired curvature, as will be seen by Figs. 3 and 4.

i is the sheet of glass paper or other grinding material the ends of which are held to the outer ends of the frame a by clamping bars 70, and thumb-nuts 73 the sheet being tightly stretched over the curved surface of the block it and traveling backward and forward over the same by the action of the lever f.

Z is the cross plate holding the brush in position for grinding by the wing nuts and pivoted at Z to the two brackets m, n fixed to the side frames (Z. n is the radial slot formed in each. of the said brackets and through which passes a wing-nut 0 for fixing the plate at the desired angle.

p is the adjustable guide or block fixed to the plate Z by the wing-nut In order to grind the brush to the desired angle it is held by the operator with its lower end resting upon the glass-paper passing over the block it at such angle. The cross plate Z is then turned so as to be in close cont-act with the side of the brush and the cross plate is fixed in this position by the wing nuts 0 The block p is also adjusted so as to bear against one end of the brush where it is fixed by the wing nut g for preventing endwise shifting of the brush after which the lever Z is worked backward and forward thus producing the backward and forward travel of the glass paper 2' over the surface of the block it and underneath the brush so as to grind the latter evenly and to the correct angle desired.

I claim:

1. Machine for grinding the contact surfaces of carbon brushes for dynamos comprising stationary side plates, a cross piece fast between the side plates, a form block mounted on said cross piece, a two-armed rocking frame pivoted between the side plates, a pliable grinding medium clamped to the rocking frame and stretched over the form-block, an operating handle for the rocking frame, extension cheeks fast on the side plates above the form-block, an adjustable cross plate held edgeWise between said cheeks, and means for adjusting the angularity of said cross-plate, as set forth.

2. A machine for grinding carbon brushes, consisting of a stationary frame, a form block fast in said frame, a rocking frame, a grinding band and a handle attached to said rocking frame, slotted extension cheeks fast on the stationary frame, and a pivoted adjustable plateheld fast in said slotted extension cheeks, as set forth.

ALFRED VATKINS.

WVitnesses:

J 0s. MATWIN, F. GYLEs.

Copies of this patent may be obtained for five cents each, by addressing the Commissioner of Patents, Washington, D. C. 

